1. Field of the Invention
The present invention relates to a method for separating magnetic particles mixed in a fluid by making use of the action of magnetic attraction, wherein the method includes causing the magnetic particles dispersed in an original fluid such as liquid or gas to be attached magnetically by the magnetic attraction, and separating those magnetic particles from the fluid. The present invention also provides a separating system and a separator that attract the magnetic particles in the fluid magnetically and separates them from the fluid by operating in accordance with the steps of such method.
2. Prior Art
There is a conventional separator that is used to separate ferromagnetic metals by attracting the metals in a particular object such as a fluid magnetically and separating them from the object.
It is also known that even for certain magnetic substances, other than the ferromagnetic substances, that possess less magnetization when placed in a magnetic field (referred hereinafter to as xe2x80x9cless magnetic substancesxe2x80x9d or xe2x80x9cless magnetic particlesxe2x80x9d), they may be attracted magnetically and separated if the magnetic force that is applied is increased. A process is also proposed, which deals with fine white day, such as kaolin, whose composition contains magnetic impurities, and allows those magnetic impurities to be removed by making use of the energy of the applied magnetic field (as disclosed in Japanese patent Publication No. 63- 95908).
In the mineral dressing field where foreign ferromagnetic substances or elements contained in a particular mineral and that should be removed are attracted magnetically and separated from the mineral, or in the field where foreign ferromagnetic objects such as works are attracted magnetically and separated from objects such as works being processed, there is a process that is used to separate those foreign substances or elements, or works by separating them by attracting them magnetically. In this process, the separation occurs by making one side of an electromagnet in contact with objects being processed, thereby magnetizing and attracting any foreign objects magnetically, and then rotating the electromagnet to demagnetize the magnetically attracted portions of those objects. However, this process is primarily designed to separate the foreign ferromagnetic substances or elements, or works, by the magnetic attraction, and is not suitable for use in separating less magnetic substances or elements, or works, that possess less magnetization when placed in a certain magnetic field. The process as mentioned above that utilizes the energy of the normal magnetic field to process the kaolin composition cannot be used for separating any less magnetic substances or elements.
Those less magnetic substances or elements require a powerful magnetic force (or example, 1000 Gauss or more) to be magnetized and attracted magnetically, and the substances or elements that have thus been magnetized and attracted must be removed before they become saturated magnetically. When a powerful magnetic force is applied, it is difficult to remove the residual magnetism that remains in the magnetized substances or elements, shortly after the magnetic field is removed by cutting the electrical current. Thus, this process has several problems in that it cannot be utilized for the industrial applications. For example, even when the less magnetic substances or elements are magnetized and attracted by applying the powerful magnetic force of 1000 Gauss or more across them, if there are any less magnetic substances or elements that are attached to the magnetized surface, other less magnetic substances or elements that make contact with those less magnetic substances or elements will not be magnetized and attracted, and will be allowed to flow away without being attracted magnetically at all. Thus, this process is not efficient in separating the less magnetic substances or elements. This problem may be solved if the less magnetic substances or elements that have been magnetized and attached by the magnetic attraction are to be removed frequently. It is difficult to remove those substances or elements in a short time, however, because the residual magnetism remains in them. Accordingly, the separating process must be suspended until the residual magnetism disappears, each time the substances or elements that are attached by the magnetic attraction are to be removed completely. This prevents the efficient separation.
The present invention solves the aforementioned problems of the prior art by providing a method for separating magnetic particles in a fluid, which comprises the steps of feeding an original fluid containing magnetic particles dispersed therein into a magnetized tube as an object being processed (referred hereinafter to as xe2x80x9cobject fluidxe2x80x9d), rotating the magnetized tube, adding free ferromagnetic elements into the tube as required to increase the effective magnetized surfaces within the tube, thereby making effective use of the magnetized surfaces, attracting the magnetic particles magnetically to the magnetized surfaces, demagnetizing the magnetized surfaces before they reach their magnetic saturation, feeding an exhaust fluid into the tube, and removing the magnetically attracted magnetic particles from the demagnetized surfaces by carrying them with the exhaust fluid. According to the method, several magnetized tubes may be provided in parallel, and those individual tubes may be operated so that the magnetic attraction of the magnetic particles and the removal of the magnetic particles thus attracted magnetically can occur alternately for each individual tube. In this way, at least any one of those tubes may be kept running at any time without having to discontinue the separating process, and the separating efficiency may be improved accordingly.
In one aspect of the present invention, a method is provided for separating magnetic particles, which includes the steps of feeding an original fluid containing magnetic particles dispersed therein into a magnetized tube as an object being processed (also called xe2x80x9cobject fluidxe2x80x9d), allowing the magnetic particles in the object fluid to be attached to the magnetized surfaces within the tube by the magnetic attraction, and removing the magnetic particles from the magnetized surfaces by demagnetizing the tube, wherein the method is characterized by the fact that the magnetic attraction of the magnetic particles to the magnetized surfaces within the tube occurs by rotating the tube.
In another aspect of the present invention, a method is provided for separating magnetic particles, which includes the steps of feeding an original fluid containing magnetic particles dispersed therein into a magnetized rotary tube as an object being processed (also called xe2x80x9cobject fluidxe2x80x9d), allowing the magnetic particles in the object fluid to be attracted magnetically to the magnetized surfaces within the tube, suspending the feeding of the object fluid before the magnetic attracting capability of the magnetized surfaces within the tube becomes lower below a certain value, demagnetizing the magnetized surfaces within the tube, feeding an exhaust fluid into the tube under the applied pressure for carrying the detached magnetic particles therewith, removing the magnetic particles together with the exhaust fluid from the tube, and separating the magnetic particles from the exhaust fluid that contained the magnetic particles therein. In this case, the exhaust fluid may be clean water or air, and may be fed into the tube in the direction opposite to that in which object fluid is fed. The surfaces being magnetized may include both the inner wall of the tube and the surfaces of the free ferromagnetic substances or elements that may be added as required into the tube.
In a further aspect of the present invention, a system is provided for separating magnetic particles mixed into an original fluid, which comprises means for crashing an original object into fine particles, if the object is in its solid form and then dispersing the fine particles in water or other fluid, means for adjusting the density of an original object to an appropriate level if the object is originally a fluid, means for feeding either of the resulting object fluids into a magnetized rotary tube as an object being processed (also called xe2x80x9cobject fluidxe2x80x9d), means for allowing the magnetic particles contained in the object fluid to be attracted magnetically to the magnetized surfaces within the tube, means for demagnetizing the magnetized surfaces within the tube, means for feeding an exhaust fluid under the applied pressure into the tube for carrying the detached magnetic particles therewith, means for removing the detached magnetic particles together with the exhaust fluid from the tube, and means for separating the magnetic particles from the exhaust fluid. The tube may be divided into several tube sections, each of which may provide a magnetic force of different strength. Specifically, the strength of the magnetic force may be increasing gradually from the tube section located on the inlet side of the tube toward the tube section located on the outlet side. In other words, the strength is the smallest at the inlet side section, and is the greatest at the outlet section. The exhaust fluid may be clean water or air, or combination of both. The rotary tube may be a round tube, to which mechanical means for rotating the tube may be connected.
In still another aspect of the present invention, an apparatus is provided for separating magnetic particles mixed into a fluid, which includes a plurality of tubes arranged in parallel on a machine base, each of the tubes is rotatably connected on its one end to a feed pipe for feeding an original fluid containing magnetic particle into each respective tube as an object being processed (referred hereafter to as xe2x80x9cobject fluidxe2x80x9d). And each of the tubes is rotatably connected on its other end to a delivery pipe for removing the object fluid from which the magnetic particles have been separated. A pressurized fluid delivery pipe connected to the outlet pipe via a check valve, a further pressurized fluid delivery pipe connected to the above pressurized fluid delivery pipe for delivering a different pressurized fluid, an outlet pipe connected to the above inlet delivery pipe via a control valve for discharging the magnetic particles separated from the fluid carrying the magnetic particles therewith, and means for rotating the rotary tube. Each of the tubes includes a plurality of tube sections connected in series, each of which has a magnetizing coil winding around the outer periphery thereof. A control device is coupled with each of those magnetizing coil windings for controlling the strength of the magnetic force provided by the magnetizing coil winding. The free ferromagnetic substances or elements may be iron or iron alloy, which may be formed into small pieces having the rugged surfaces. The quantity of those small pieces to be fed into the tube sections may be controlled so that the apparent quantity can be equal to any value between 30% and 90% of the total volume of the tube sections. The number of the parallel tubes may be two, four, or six, depending on the particular requirements.
The electrical current that can flow through each coil winding that act as an electromagnet is preferably DC current, which is preferably supplied from any voltage-controlled power supply. The fluid that may be used for the purposes of the present invention is usually liquid (water) for the easiness in handling. When an original fluid being processed is any gas (such as exhaust gas produced by burning), the separation may occur directly from the gas. In this case, air is often used as the pressurized exhaust fluid, but in some cases, water or any liquid containing any medicine may also be used.
Most commonly, the tube may be a round tube, but instead of the round pipe, other shapes such as elliptical may be used. The choice should be made by taking into account the fact that the tube rotates. For example, a tube having a particular shape in cross section, such as annular corrugated shape (contiguous rugged arcs) may be used to increase the contact area with the fluid being processed. The diameter and length of the tube may be determined, depending on the respective properties of an original fluid being processed and magnetic particles contained in the original fluid, and should usually be 5 cm to 50 cm in diameter and 100 cm to 300 cm in length, respectively, for the efficient separation of the magnetic particles from the original fluid.
According to the present invention, the flow rate of an original fluid being processed (also called xe2x80x9cobject fluidxe2x80x9d) may also be determined, depending upon the respective properties of the original fluid and magnetic particles contained in the fluid, and the particular requirements for the diameter and length of the tube. It should usually be 1 cm/sec to 50 cm/sec. Similarly, the number of rotations for the tube may be determined, depending upon the respective properties of the original fluid and magnetic particles contained in the fluid as well as other requirements. It should usually be 1 rotation/sec to 10 rotations/sec, which may depend upon the particular original fluid being processed.
According to the present invention, the tube may externally be divided into several tube sections, each of which may have a coil winding around the outer periphery thereof. The strength of the magnetic force provided by each of the coil windings may be varied for each respective tube section, by changing the current flow through the respective coil winding and by changing the amount, or the number of turns, of the respective coil winding. Specifically, the strength of the magnetic force may be varied for each tube section such that it is increasing gradually from the first tube section on the inlet side of the tube toward the last section on the outlet side. In this way, an original fluid being processed may contain different types of magnetic particles of different magnitudes, which may be attracted magnetically by the different tube sections when they are flowing though the tube sections of the tube. Thus, the whole tube may be used as a magnet filter.
For example, the ferromagnetic particles such as iron particles may be attracted magnetically by the first tube section that provides the low magnetic force, some less magnetic particles such as Ca, Mg may be attracted magnetically by the following tube section that provides the medium magnetic force (for example, 1.000 Gauss to 10000 Gauss), and other more less magnetic particles (such as gold, nitrogen) may be attracted magnetically by the final section that provides the high magnetic force (over 10000 Gauss). When the original fluid containing magnetic particles of different types and strengths flows through those tube sections, the sections may be magnetized and demagnetized alternately from one section to the following section. The different magnetic particles that have been attracted magnetically by each corresponding section may be collected in each section, which is now demagnetized, by an exhaust fluid that is fed under the applied pressure into the tube.
For instance, when an original fluid or liquid that contains burned ashes solved by water is to be processed in accordance with the present invention, the components such as iron, manganese, etc. may be attracted magnetically by the tube section that provides the low magnetic force, the components such as Mn, Cr, Pd, etc. may be attracted magnetically by the tube section that provides the medium magnetic force, and the components such as dioxin, Cd, Ag, etc. may be attracted magnetically by the tube section that provides the high magnetic force. Thus, all of the less magnetic particles may be magnetized, demagnetized, and then separated from the original fluid or liquid with the higher efficiency.
According to the present invention, a mixture composed of a fluid (liquid or gas) and magnetic particles may be fed as an object being processed (also called xe2x80x9cobject fluidxe2x80x9d) into a magnetized rotary tube, the magnetic particles may be attracted magnetically within the tube, the rotary tube may be demagnetized after the feeding of the object fluid is stopped, and an exhaust fluid may then be fed into the tube under the applied pressure. The magnetic attraction and removal of the magnetic particles may be performed automatically by magnetizing and demagnetizing the inner wall of the tube or any ferromagnetic elements within the tube, respectively.
According to the present invention, a plurality of parallel tubes may be provided, and those parallel tubes may be operated alternately so that at least any one of the tubes can always be kept running at any time so that the separation can occur. Thus, the present invention may be utilized for the industrial applications. The free ferromagnetic substances that are fed into the tube may help even certain less magnetic particles be attracted magnetically. Thus, those less magnetic particles can be separated with high reliability.
According to the present invention, an original fluid that contains the magnetic particles may be fed into the magnetized rotary tube as an object being processed (also called xe2x80x9cobject fluidxe2x80x9d), and then the magnetized rotary tube may be rotated so that the magnetic attracting action can be utilized to its full ability. Thus, the separating efficiency can be enhanced.
According to the present invention, the magnetic particles that have been attracted magnetically within the tube may be removed from the tube by demagnetizing and counterflow-cleaning the tube, before the magnetic attraction becomes lower below a certain value. Thus, the continuous operation may be achieved with the same efficiency.
According to the present invention, the separation can occur continuously by running a plurality of separator tubes in parallel. When the operation for the magnetic attraction would take longer to be completed than the operation for the counterflow-cleaning, one separator tube may be counterflow-cleaned while the other separator tubes may be kept running. Conversely, the operation for the counterflow-cleaning would take longer to be completed than the operation for the magnetic attraction, one separator tube may be kept running while the other separator tubes may be counterflow-cleaned. In either case, at least one separator tubes can always be kept running at any time, and the overall efficiency can be enhanced accordingly.